The invention relates to a device for performing exothermic catalytic gas reactions for the synthesis of ammonia or methanol. The device is comprised essentially of a high-pressure shell; an upper cover; and an insert with at least two superimposed annular cylindrical catalyst containers each having a gas-permeable inner and outer wall to provide for the radial flow of gas from the outside towards the inside and with two tubular gas/gas heat exchangers arranged centrally relative to the first and second catalyst containers.
The catalytic high-pressure synthesis for producing ammonia and methanol is an exothermic process. To obtain an optimum reaction, i.e. an optimum conversion yield, it is critical that the process be conducted in an ideal temperature range. The most favorable reaction temperatures can be maintained by cooling the gases heated during the reaction through indirect heat exchange with freshly introduced gas. As the fresh gas must be delivered to the first catalyst bed at a temperature of above 300.degree. C., the fresh gas will best be heated by hot reaction gas in indirect heat exchange.
Cooling of the reaction gas may be accomplished either by providing for the reaction to take place at an almost constant temperature, as this is practiced in catalyst tube furnaces or full-space furnaces with cooling coils in the catalyst mass, or by reducing the temperatures stepwise at the outlets of the individual catalyst beds of the entire catalyst mass.
Numerous devices, i.e. furnaces, are known to be used for fulfilling the above requirements. It is known, for instance, to arrange the catalyst mass in several superimposed beds with tubular heat exchangers installed between the beds for heating the fresh gas and for reducing the reaction temperatures.
Referring to German patent application No. DE-OS 30 26 199, an axial/radial flow reactor with centrally arranged heat exchangers is shown. In this reactor, the cold fresh gas flows upwards through the tubes of the individual heat exchangers, while the hot reaction gas flows on the shellside. Each heat exchanger is arranged centrally in the lower part of the annular catalyst basket. Catalyst basket and heat exchanger are installed in such a way that the heat exchanger can only be dismantled after the catalyst basket has been emptied and removed. Furthermore, an elastic link has to be provided between the individual heat exchangers which must first be loosened to avoid damage before one is able to dismantle the heat exchanger. In replacing the catalyst, it is not possible to remove the catalyst basket downward in the reactor. The fact that, prior to dismantling a heat exchanger, the catalyst basket has first to be removed is reason for having to design the upper cover extending over the entire cross-section of the high-pressure shell. A cover of reduced diameter cannot be used.
Other known types of furnaces with heat exchangers integrated in the catalyst beds generally have the disadvantage that they require components which are complicated and difficult to replace and that they encounter sealing problems due to the high temperature and pressure differences generated during operation of an ammonia or methanol synthesis plant.